Note: Descriptions are shown in the official language in which they were submitted.
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PRODUCTION OF PATTERNED ABRASIVE SURFACES
Background of the Invention
° 5 This invention relates to the production of patterned
abrasive surfaces on substrates in a form useful for fine
finishing of substrates such as metals, wood, plastics and
glass.
The proposal to deposit isolated structures such as
islands of a mixture of a binder and abrasive material
on
a backing material has been known for many years. If the
islands have very similar heights above the backing and
are adequately separated then, (perhaps after a minor
dressing operation), use of the product will result in
reduced surface scratching and improved surface
smoothness. In addition the spaces between the islands
provide a route by which swarf generated by the abrasion
can be dispersed from the work area.
In a conventional coated abrasive, investigation of
the grinding surface reveals that a comparatively small
number of the surface abrasive grits in an active abrading
zone are in contact with the workpiece at the same time.
As the surface wears, this number increases but equally
the utility of some of those abrasive grits may be reduced
by dulling. The use of abrasive surfaces comprising a
uniform array of isolated islands has the advantage that
the uniform islands wear at essentially the same rate such
that a uniform rate of abrasion can be maintained for
longer periods. In a sense the abrading work is more
evenly shared among a larger number of grinding points.
Moreover since the islands comprise many smaller particles
of abrasive, erosion of an island uncovers new, unused
abrasive particles which are as yet undulled.
One technique for forming such an array of isolated
islands or dots that has been described is that of the
rotogravure printing. The technique of rotogravure
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printing employs a roll into the surface of which a
pattern of cells has been engraved. The cells are filled
with the formulation and the roll is pressed against a
surface and the formulation in the cells is transferred to
the surface. Normally the formulation would then flow
until there was no separation between the formulations
deposited from any individual cell. Ultimately a layer of
essentially uniform thickness would be obtained. By way
of illustration, comparative Examples C and D of United
States Patent No. 5,152,917 describe a process in which
the pattern obtained by a rotogravure process quickly lost
all separation of the individual amounts deposited from
the cells.
In United States Patent No. 5,014,468 a binder/
abrasive formulation was deposited from rotogravure cells
on a roller in such a way that the formulation was laid
down in a series of structures surrounding an area devoid
of abrasive. This is believed to be the result of
depositing less than the full volume of the cell and only
from the perimeter of each cell, which would leave the
ring formations described.
The problem with the rotogravure approach has
therefore always been the retention of a useful shape
to the island. To formulate an abrasive/binder mixture
that is sufficiently flowable to be deposited and yet
sufficiently non-flowable such that it does not slump to
an essentially uniform layer coating when deposited on a
substrate has proved very difficult.
Chasman et al., in United States Patent No. 4,773,920
disclosed that using a rotogravure coater, it is possible
to apply a uniform pattern of ridges and valleys to the
binder composition which, when cured, can serve as
channels for the removal of lubricant and swarf. However
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beyond the bare statement of possibility, no details are
given that might teach how this might be carried out.
In United States Patent No. 4,644,703 Kaczmarek
et al. used a rotogravure roll in a more conventional
fashion to deposit an abrasive/binder formulation to
deposit a layer that is then smoothed out before a second
layer is deposited by a rotogravure process on top of the
smoothed-out first layer. There is no teaching of the
nature of the final cured surface.
In United States Patent No. 5,014,468 (Ravipati
et al.) it was proposed to use an abrasive/binder mixture
having non-Newtonian flow properties and to deposit this
mixture by a rotogravure technique on to a film. In this
process the mixture was deposited from the edges of the
rotogravure cells to produce a unique structures with
deposits of reducing thickness with distance away from the
surface surrounding areas devoid of the mixture. If the
cells are sufficiently close together, the surface
structures can appear interlinked. This product has
proved very useful, particularly in ophthalmic fining
operations. The process is very useful but it has a
potential problem with increasing build-up of material in
the cells of the rotogravure roll such that the deposition
pattern can change slightly during a protracted production
run. In addition the nature of the process is such that
it is limited to formulations containing relatively fine
abrasive grits, (usually less than 20 microns?.
Another approach has been to deposit the
abrasive/binder mixture on a substrate surface and then
impose a pattern comprising an array of isolated islands
on the mixture by curing the binder while in contact with
a mold having the inverse of the desired patterned
surface. This approach is described in United States
Patent Nos. 5,437,754, 5,378,251, 5,304,223 and
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5,152,917. There are several variations on this theme
but all have the common feature that each island in the
pattern is set by curing the binder in contact with a
molding surface. This approach too is not without its
problems in that incomplete pull-out from the mold often
occurs such that, instead of producing, for example
pyramids, volcano shapes complete with crater, frequently
result.
The present invention presents a technique for
producing uniformly patterned shapes of an abrasive/binder
combination that does not require a cure-in-mold operation
or the selection of a binder/abrasive combination with
specific non-Newtonian flow characteristics.
The present invention therefore provides a flexible
and effective route for the commercial scale production
of coated abrasives with a uniform array of isolated
abrasive composite shapes. Such coated abrasives are well
adapted to the treatment of a wide range of substrates to
yield fine finishes for protracted periods of operation at
a substantially uniform cut rate.
General Description of the Invention
The problem encountered in the use of rotogravure
techniques to produce patterned coated abrasive materials
has always been the retention of a useful shape and
pattern after the deposition of the formulation. Most
frequently the deposited shape loses its vertical
dimensions and tends to run across the surface and join up
with adjacent shapes. This problem is referred to in
comparative Examples C and D of United States Patent
No. 5,152,917 which was discussed above. In United States
Patent No. 5,014,468, the solution adopted therein was to
use a formulation with a shear thickening rheology which
caused the mixture to be deposited from the edges of the
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rotogravure cells to form the unique pattern described
therein.
It has now been found that an abrasive/binder
formulation can be deposited on a substrate and a pattern
produced on the formulation surface by an embossing
process if the rheology of at least the surface layer of
the deposited formulation is modified before embossing.
This embossed pattern can then be cured to maintain the
embossed structure
Theoretical studies of the pattern retention of
deposits indicate that surface tension is the driving
force leading to flow (and hence loss of the pattern),
and viscosity is the resisting force. Thus retention of
the pattern will be favored by low surface tension and
high viscosity. However with radiation-curable binders
such as are commonly used with the abrasive/binder
fozmulations with which this invention is primarily
concerned, the surface tension does not vary much and
is generally in the range of about 30-40 dynes/cm.
A properly formulated water-based abrasive/binder mixture
also generally has a surface tension in the same range.
Thus the viscosity is the most result-affecting parameter
which can be adjusted.
The present invention therefore comprises a process
for the production of a coated abrasive comprising a
pattern of abrasive/binder composites adhered to a backing
material said process comprising:
(a) depositing a slurry formulation comprising
abrasive grits (and optionally fillers, grinding aids,
and other additives), and a curable resin binder on a
substrate in a continuous or patterned manner;
(b) treating the deposited formulation to
render at least the surface portion of the formulation
plastic but non-flowing;
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(c) embossing a pattern upon the binder/
abrasive formulation; and subsequently
(d) curing the binder component of the
formulation to retain said pattern.
The key to this process is the treatment to render at
least the surface portion of the formulation plastic but
non-flowing. By this it is meant that the surface is
sufficiently plastic that it can be embossed using an
embossing tool but that it will substantially retain the
embossed shape for at least 30 seconds after removal of
the embossing tool. A shape is considered to have been
"substantially retained" if the vertical height of the
embossed shape above the substrate does not decrease by
more than 10%.
Prior to embossing, the viscosity of the
binder/abrasive formulation is modified in such a way as
to limit the flow that would tend to occur at the lower
viscosities at which the formulation is conventionally
deposited. It is, however, not necessary that the
viscosity of the whole of the formulation be adjusted to
the higher level. It is often sufficient if the outer
exposed portion quickly attain the higher viscosity since
this can then act as a skin so as to retain the embossed
shape even if the inner portion retains a relatively lower
viscosity for a longer period.
Viscosity modification of at least the surface layers
can be achieved for example by incorporating in to the
formulation a volatile solvent that is rapidly lost when
the formulation is deposited on the backing material,
perhaps with the assistance of an increased ambient
temperature or by a localized blast of hot gas.
Temperature of course can also affect the viscosity.
It is, therefore, important to balance these competing
effects to ensure that the result is increasing viscosity.
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One factor assisting in this direction would be a tendency
for increased temperature to cause accelerated curing
in the case of thermally curable resin systems. Another
option would be to decrease the temperature of the
structure such that the viscosity is increased. This
could be done for example by passing the substrate with
the layer of deposited formulation thereon under a chilled
roll and/or under a cold gas flow.
In addition to adjustment by change of temperature or
removal of liquid, it is possible to change the viscosity
by increasing the solids loading. In general, it is
sufficient that the surface layer achieve the higher
viscosity so as to hold a shape subsequently embossed
thereon. Thus applying a finely divided "functional
powder" on to the surface of the structure will act to
form a localized "skin" of increased viscosity upon the
structure causing it to retain an imposed shape until cure
renders the shape permanent.
In the present application the term "functional
powder" is used to refer to finely divided, (that is, with
an average particle size, DSO, of less than 250
micrometers), material that modifies the properties of the
formulation. This can be as simple as a viscosity
modification or an improved property in the cured
formulation such as grinding efficiency. The functional
powder can also act to serve as a releasing agent or a
barrier between the resin formulation and the embossing
tool, reducing sticking problems and allowing improved
release from the embossing tool.
The powder can be applied in the form of a single
layer on top of the abrasive/binder composite or in
several layers to form a structured composite having
unique grinding properties. This is in fact an
' advantageous and preferred aspect of the invention.
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The powder itself can be an abrasive or a variety
of powdered materials, or a combination of the previous,
conferring advantageous properties. Abrasive grains
usable as the functional powder can consist of any
type of abrasive grain and grit size which in some
instances may differ from that of the grain used in the
adhesive formulation and can lead to unique grinding
characteristics. The functional powder can also consist of
any of the family of grinding aids, antistatic additives,
any class of fillers, and lubricants.
The deposition of the functional powder layers)
can be done using a variety of conventional deposition
methods. These methods include gravity coating, electro-
static coatings, spraying, vibratory coatings, etc. The
deposition of varying powders can occur simultaneously or
in an ordered fashion to create a composite structure
before embossing.
In one preferred embodiment of the invention the
deposition of the abrasive/binder slurry formulation on
the backing can be done in two or more layers. Thus for
example it is possible to deposit initially a slurry
formulation with a first abrasive grain and then deposit
on top a second layer with a different abrasive grain.
The grain content of the upper layer could then be made
higher, or of a superior quality, than the grain in the
lower layer. Alternatively, or perhaps additionally,
the upper layer could be provided with a grinding aid
component whereas the lower layer has none. Such
approaches, and others that are similar that can readily
be conceived, allow the coated abrasive product to grind
more efficiently. This is because, when a structured
abrasive comprising isolated abrasive/binder composites
is formed in the embossing stage, the portions of the
composites which actually are in use before the coated
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abrasive product is discarded are typically the portions
furthest removed from the backing material. It would
therefore make sense to avoid putting expensive abrasive
grain in the bottom portion of the composite and have the
larger abrasive content near the exposed surface of the
composite. The same reasoning would lead the instructed
reader to concentrate any grinding aid added near the
upper surface of the composite structure.
It is also possible to provide that, where
the formulation is deposited in a plurality of layers,
the upper layer is itself of a more viscous formulation,
perhaps as a result of the addition of higher concen
trations of abrasive grains or grinding aid. This can
provide part or all of the operation in which the surface
portion of the slurry formulation is rendered plastic but
non-flowing.
After the increase in viscosity has been achieved,
the layer is embossed to impose a pattern. This pattern
can comprise isolated islands of formulation, or a pattern
of ridges separated by valleys. The patterns are
generally designed to provide an abrasive product with
a plurality of grinding surfaces equidistant from the
backing with the area of grinding surface increasing with
erosion of the layer. Between the grinding surfaces,
channels are often provided to allow circulation of
grinding fluids and removal of swarf generated by the
grinding.
Embossing can be accomplished by an embossing tool
such as a plate forced into contact with the layer of
formulation or, often more simply, the tool can comprise
a roller with the desired pattern engraved on its surface
which when contacted with the slurry formulation imposes
the reverse of the pattern engraved on the surface.
' in addition, the embossing tool can be heated or chilled
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so as to contribute to the raising of the viscosity to
render the formulation surface plastic but non-flowing.
The heating however, should not be to such a level that
the binder cures while in contact with the tooling.
By adjusting the viscosity of the resin formulation or the
surface layer, the ultimate goal is that after embossing,
the shape imposed by the embossing tool is substantially
retained for at least 30 seconds and preferably for a
minute. Most preferably the shape is retained until later
cure of the binder component can be effected.
It is often preferred that the embossed surface
is relatively tacky after the embossing such that a
functional powder can be deposited thereon before the cure
is completed such that completion of the cure causes the
functional powder to become adhered to the outer surface
of the embossed shape. Where the powder is an abrasive,
this greatly increases the aggressiveness of the initial
cut. In addition, if the powder is a grinding aid or
anti-loading additive, it is located in the optimum
position relative to the abrasive grains in the
composites. Alternatively it is possible to apply over
the embossed or perhaps over the cured and embossed
surface a fine layer of an adhesive and thereafter a
further coating of the functional powder of the kinds
discussed above. The adhesive can be of the same or
different type as is present in the abrasive/binder
formulation.
Description of the Drawings
Figs. 1-5 presented herein are SEM photomicrographs
of products made according to the process of the invention
with an abrasive slurry coated with additional abrasive
grains.
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Detailed Description of the Invention
The coating method used to place the slurry on to
a conventional substrate can comprise of a variety of
conventional coating methods including knife on roll,
knife on web, two or three roll coating, reverse roll
coating, gravure coating, slot-die coating, spraying,
curtain coating, screen printing, etc. It is important
that the slurry coating may be in the form of a continuous
coating or in a patterned fashion as would be deposited
l0 by a gravure cell. In addition, coatings may be applied
in several layers or in alternating layers with the
functional powder to achieve a composite with unique
grinding characteristics.
The embossing tool can have any desired pattern and
this is determined in large part by the intended purpose
of the coated abrasive product. It is for example
possible to provide that the tool is in the form of a
roller with surface grooves, (for example tri-helical
grooves), cut in the roll surface. This is often a very
advantageous configuration and can be adapted to produce
a pattern of diagonal stripes that is at once very
distinctive and also very effective for grinding.
Alternatively the tool may be engraved with a plurality
of cells which are reproduced as isolated islands in the
pattern imposed on the abrasive/binder layer. Many useful
surface designs can be devised, including isolated islands
of formulation or groups of patterns of islands. The
tooling itself may consist of any type of conventional
embossing moldings such as metal-plated toolings, plastic
toolings, ceramic-based toolings, etc.
. The abrasive component of the formulation can be any
of the available materials known in the art such as alpha
alumina, (fused or sintered ceramic), silicon carbide,
fused alumina/zirconia, cubic boron nitride, diamond and
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the like as well as the combination of thereof. Abrasive
particles useful in the invention typically and preferably
have an average particle size from 1 to 150 micron, and
more preferably from 1 micron to 80 micron. In general
however t:he amount; of abrasive present provides from
about 1o% to about 90%, and preferably from about 30% to
about 80%, of the weight of the formulation.
The ether ma;~ar component of the formulation is the
binder. This is a curable resin formulation selected from
radiation curable resins, such as those curable using
electron beam, UV radiation or visible light , such as
acrylated oligomers of acrylatedepoxy resins, acrylated
urethanes and polyester acrylates and acrylated monomers
including monoacrylated, multiacrylated monomers, and
thermally curable resins such as phenolic resins,
urea/formaldehyde resins and epoxy resins, as well as
mixtures of such resins. Indeed it is often convenient
to have ~~ radiat;ion curable component present in the
formulation that can be cured relatively quickly after
the formu:Lation ha:> been deposited so as to add to the
stability of the deposited shape. In the context of~this
application it is understood that the term "radiation
curable" embraces the use of visible light, ultraviolet
(W) light and electron beam radiation as the agent
bringing .about the cure. In some cases the thermal cure
functions and the radiation cure functions can be provided
by different functionalities in the same molecule. This
is often ,a desirable expedient.
The resin binder formulation can also comprise a
non-reactive thermoplastic resin which can enhance the
self-sharpening characteristics of the deposited abrasive
composites by enhancing the erodability. Examples of such
thermoplastic resin include polypropylene glycol,
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polyethylene glycol, and polyoxypropylene-polyoxyethene
block copolymer, etc.
Fillers can be incorporated into the abrasive slurry
formulation to modify the rheology of formulation and the
hardness and toughness of the cured binders. Examples of
useful fillers include: metal carbonates such as calcium
carbonate, sodium carbonate; silicas such as quartz, glass
beads, glass bubbles; silicates such as talc, clays,
calcium metasilicate; metal sulfate such as barium
sulfate, calcium sulfate, aluminum sulfate; metal oxides
such as calcium oxide, aluminum oxide; arid aluminum
trihydrate. ._
The abrasive slurry formulation .may comprise a
grinding aid to increase the grinding efficiency and cut
rate. Useful grinding aid can be inorganic based, such
as halide salts, for example sodium cryolite, potassium
tetrafluoroborate, etc.; or organic based, such as
chlorinated waxes, for example polyvinyl chloride.
The preferred grinding aids in this formulation are
cryolite and potassium tetrafluoroborate with particle
size ranging from 1 to 80 micron, and most preferably
from 5 micron to 30 micron. The weight percent of
grinding aid ranges from 0% to 50%, and most preferably
from 10-30%.
The abrasive/binder slurry formulations used in the
practice of this invention may further comprise additives
including: coupling agents, such as silane coupling
agents, for example A-.174 and A-1100' available from
Osi Specialties, Inc., organotiaanates and zireo-
aluminates; anti-static agents, such as graphite,
carbon black, and the 7.ike; suspending agents, such as
fumed silica, for example Cab-0-Sil M5~' Aerosil 200;
anti-loading agents, such as~zinc stearate; lubricants
* Trademark
~E
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such as wax; wetting agents; dyes; fillers; viscosity
modifiers; dispersants; and defoamers.
Depending on the application, the functional powder
deposited on the slurry surface can impart unique grinding
characteristics to the abrasive products. Examples of
functional powders include: 1) abrasive grains - all
types and grit sizes; 2) fillers - calcium carbonate,
clay, silica, wollastonite, aluminum trihydrate, etc.;
3) grinding aids - KBF4, cryolite, halide salt, halogenated
hydrocarbon, etc.; 4) anti-loading agents - zinc
stearate, calcium stearate, etc.; 5) anti-static agents -
carbon black, graphite, etc.; 6) lubricants -waxes,
PTFE powder, polyethylene glycol, polypropylene glycol,
polysiloxanes etc.
The backing material upon which the formulation is
deposited can be a fabric, (woven, non-woven or fleeced),
paper, plastic film or metal foil. Generally, the
products made according to the present invention find
their greatest utility in producing fine grinding
materials and hence a very smooth surface is preferred.
Thus finely calendared paper, plastic film or a fabric
with a smooth surface coating is usually the preferred
substrate for deposition of the composite formulations
according to the invention.
The invention will be further described with respect
to certain specific embodiments which are understood to be
for the purposes of illustration only and imply nc
necessary limitation on the scope of the invention.
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Abbreviations
To simplify data presentation, the following
abbreviations will be used:
Polymer Components
~ Ebecryl 3605, 3700 - acrylated epoxy oligomers available
from UCB Radcure Chemical Corp.
'~ T~T'A - trimethylol propane triacrylate available from
Sartomer Company, Inc.
DICTA - isocyanurate triacrylate available from Sartomer
Co., Inc.
*TRPGDA - tripropylene glycol diacrylate available from
Sartomer Co., Inc.
Binder Components
'~ Darocure 1173 - a photoinitiator available from Ciba-Geigy
Company
*Irgacure 651 - a photoinitiator available from Ciba-Geigy
Company
*2-Methylimida.zole - a catalyst from the BASF Corp.
*Pluron.ic 2582 - polyoxypropylene-polyoxyethylene block
copolymer available from the BASF Corp.
* ICBF4 - grinding aid with a median particle side of
approximately 20 ~,m available from Solvay.
Cab-O-Sil M5 - fumed silica from Cabot Corporation
rain
* FRP.L - fused A1a03 from Treibacher tP320 or P1000: grade
indicated by "P-number" ).
*Calcined A1203 (40 Vim) from Microabrasives Corporation.
Backinqg
3 mil. Mylar film for ophthalmic applications
5 mil. Mylar film for metalworking applications
Surlyn-coated J-weight polyester cloth
* Surlyn is an ionomer resin SURLYN 1652-1 from Du Pont.
* Trademark
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Abrasive 513~ry Formulations
Table I
Component I TI III IV
~Ebecryl 3605 19.3%
~EbeCryl 3700 6.3%
~ NVP 8 . 3 0
*ICTA 7.9% 14.7% 14%
~'TMPTA 8.1% 14.7% 14%
'~ TRPGDA 5 . 3 %
~ Irgacure 651 0 :-8%
~Darocure 1173 1.1e 0.60 0.6%
'~ 2 MI 0.20
* Cab-O-Sil 0.8%
~Silane 1.1% 0.8%
Pluronic 2582 1.4%
~ KBF 23.3% 23.3% 23.3% 23.3%
'Grain 46.70 46.7% 46.7% 46.7%
Formulation Preparation Procedure
The monomers and/or oligomer components were
mixed together for 5 minutes using a high shear mixer at
1000 rpm. This binder formulation was then mixed with any
initiators, wetting agents,~defoaming agents, dispersants
etc. and mixing was continued fvr 5 minutes further at
the same rate of stirring. Then the following components
were added, slowly and in the indicated order, with five
minutes stirring at 1500 rpm between additions: suspension
agents, grinding aids, fillers and abrasive grain. After
addition of the abrasive grain the speed of stirring was
increased to 2,000 rpm and continued for 15 minutes.
* Trademark
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During this time the temperature was carefully monitored
and the stirring rate was reduced to 1,000 rpm if the
temperature reached 40.6°C.
D~~osition of the Formulation
The resin formulation was coated on to a variety
of conventional substrates listed previously. In the
cited cases the abrasive slurry was applied using a knife
coating with the gap set at desired values. Coating was
done at room temperatures.
Application of Functional Powders and Embossina
Before embossing, the surface layer of the slurry was
modified with abrasive grits with the same particle size
or finer than that used in the formulation. Enough was
deposited to form a single layer adhered by the uncured
binder component. Excess powder was removed from the
layer by vibration. Application of the powder was by a
conventional, vibratory screening method.
Once the substrate had been coated with the uncured
slurry formulation and the functional powder applied,
an embossing tool with the desired pattern was used to
impart the desired shape to the abrasive resin and grain
formulation. This embossing setup included a steel
backing roll which imparted the necessary support during
the application of pressure by the steel embossing roll.
A wire brush setup was used to remove any dry residue or
loose grains remaining in the cells after the tool had
imparted its impression on to the viscosity modified
formulation.
Cure
After the pattern was embossed into the viscosity-modified
layer, the substrate was removed from the embossing
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tooling and passed to a curing station. Where the cure
is thermal, appropriate means are provided. Where the
cure is activated by photoinitiators, a radiation source
can be provided. If W cure is employed, two 300 watt
sources are used: a D bulb and an H bulb with the dosage
controlled by the rate at which the patterned substrate
passed under the sources . In the case of the matrix of
experiments listed in Table 2, the cure was by UV light.
In the case of the Formulation I, however, W cure was
immediately followed by a thermal cure. This curing
process was adequate to ensure final dimensional
stability.
In the first example, the layer was embossed by a
roll having cells engraved therein in a 17 Hexagonal
pattern. This produced the pattern of hexagonal shaped
islands shown in Figs. 1 and 2. In each, an abrasive grit
was dusted on the surface to serve as the functional
powder. In Fig. 1 the abrasive dusted on the surface was
P1000 and in Fig. 2 it was P320. In each case the
abrasive/binder formulation was Formulation I.
In the second example, the embossing roll was
engraved with a 25 Tri-helical roll surface pattern of
grooves. Figs. 3 and 4 show Formulations III and IV as is
used in the first experiment coated with P320 and P1000
abrasive grits respectively. The same coating technique
was used.
In a third example, the pattern engraved on the
embossing roll was 45 Pyramid with Formulation I giving a
pattern of isolated square-based pyramids. The surface
was modified by application of P1000 grit over the same
formulation used in the first and second experiments.
The result is shown in Fig. 5.
In all three experiments, the structures on the
embossed surface remained essentially unchanged from the
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time of the embossing to the time the binder component was
fully cured.
Additional examples, similar in shape but varying in
formulation and abrasive content were also carried out as
listed in Table 2. In all cases, the manufacturing
process is identical to the first three examples; however,
variations were made in the resin composition and
functional powders.
T9hle 2
' Slurry
Resin Thick Grain
Embossed ips Formula- mss in unctional
xample Pattern /Irr~hlion (mils) Siurry Powder
1 Hexagonal17 I 5 P320 P1000
2 Hexagonal17 I 8 P320 P1000
3 Hexagonal17 I 10 P320 P1000
4 Hexagonal17 I 10 P320 P320
5 Tri-Helical25 II 7 P320 P320
6 Tri-Helical25 I 7 P320 P320
~ Tri-Helical25 I 7 P320 P1000
8 Tri-Helical25 III 7 P320 P320
9 Tri-Helical25 III 7 P320 P320+KBF4
10 Tri-Helical25 III 7 40 ~.m 40 ~m
11 Tri-Helical25 IV 7 40 P.m 40 ~cm
12 Tri-Helical40 III 5 P320 P320+KBF,
13 Tri-Helical40 III 5 40 um 40 ~m
14 Tri-Helical40 IV 5 40 gm 40 N.m
15 Pyramidal45 I 5 P320 P1200
16 Pyramidal45 I 7 P320 P1200
3 0 17 Pyramidal45 I 7 P320 P320
18 Pyramidal45 I 10 P320 P1000
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The 17 Hexagonal embossing roll pattern
comprised cells 559 microns in depth with equal sides of
1000 microns at the top and 100 microns at the bottom.
The 25 Tri-helical pattern comprised of a continuous
channel cut at 45 degrees to the roll axis that has a
depth of 508 microns and top opening width of 750 microns.
The 40 Tri-helical pattern comprised of a
continuous channel cut at 45 degrees to the roll axis that
has a depth of 335 microns and a top opening width of
425 microns.
The 45 Pyramidal pattern comprised a square-based,
inverted pyramid shaped cells with a depth of 221 microns
and a side dimension of 425 microns.
Grinding Tests
Several of the listed samples were subjected to
two primary forms of grinding testing with the data listed
in Tables 3-5. The first forth of testing consisted of
Schieffer testing up to 600 revolutions with an 8 lbs. of
constant load on a hollow, 304 stainless steel workpiece
with a 1.1 inch O.D. which gives a effective grinding
pressure of 23.2 psi. The patterned abrasive was cut into
disks of 4.5" diameter and mounted to a steel backing
plate. Both the backing plate and the workpiece rotate in
a clockwise fashion with the backing plate rotating at
195 rpm and the workpiece rotating at 200 rpm. Workpiece
weight loss was noted every 50 revolutions and totaled at
the end of 600 revolutions.
The second method of testing consisted of a
microabrasive ring testing. In this test, nodular cast
iron rings (1.75 inch O.D., 1 inch I.D. and 1 inch width),
were pre-roughened using a 60 ~,m. conventional film
product and then ground at 60 psi. with the patterned
abrasive. The abrasive was first sectioned into 1" width
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strips and was held against the workpiece by rubber shoes.
The workpiece was rotated at 100 rpm and oscillated in
the perpendicular direction at a rate of 125 oscillations/
,
minute. All grinding was done in a lubricated bath of
OH200 straight oil. Weight loss was recorded every 10
revolutions and totaled at the end of the test.
Table 3 Schieffer Testing of Patterned Abrasives
with FRPL P320 grain in Slurry Formulation.
(500 Revolutions)
Grain in Functional Total Cut
Example Pattern Slurry Powder ( % of Control)
18 45 Pyramid P320 P1000 100%
(control)
3 17 HexagonalP320 P1000 104%
4 17 HexagonalP320 P320 113
8 25 Tri-HelicalP320 P320 115 %
9 25 Tri-HelicalP320 P320+KBF, 143
Table 4 Schieffer Testing of Patterned Abrasives with
Calcined A1203 40 ~,m Grains in Slurry
Formulation. (600 (Revolutions)
Grain in F~mctional Total Cut
Slurry Powder
( 96 Control)
C-1 (Conuol)None NIA NIA 100 %
3 10 25 Tri-Helical40 pm 40 N,m 131
0
i3 40 Tri-Helical40 ~m 40 Eem 110%
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Table 5 Ring Testing for Microfinishing Application
(50 Revolutions at 60 psi.)
Grain in Functional Total Cut
Example Pamern Slucry Powder ( 96 of
Control)
C-1 (Control)None NIA NIA 100
25 Tri-Helical40 ~.m 40 ~cm 109%
In Table 3, the effect of the type of functional
powder and pattern is clearly demonstrated. With the
45 Pyramid (P320 in the formulation and P1000 as the
functional powder) as the control, using a larger
15 17 hexagonal shape pattern the same resin formulation
and functional powder resulted in a slight increase in
total cut. In all cases where the P1000 was substituted
with a coarser P320 grade, the cut was further increased.
In addition, the tri-helical pattern outperformed the
20 hexagonal pattern. In the final case where the functional
powder consisted of a blend of KBF4 and P320, the cut was
dramatically increased. From this set of data it can be
clearly seen that the pattern type coupled with the type
of functional powder clearly alters the grinding
characteristics.
In Table 4, the patterned abrasives were compared
to comparative example C-1, a 40 ~.m grit conventional
microfinishing abrasive under the trade name of Q151
from Norton Company. It can be observed in both patterned
abrasives, the total cut was increased significantly
over the conventional product with the 25 Tri-helical
outperforming the finer 40 Tri-helical pattern.
In Table 5, the 40 ~.m patterned abrasives were
compared in a microfinishing application. Once again,
compared to the comparative example C-1, a conventional
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abrasive product under the trade name of Q151 from
Norton Company, the patterned abrasive demonstrates an
improvement in the total cut. Overall, the above patterns
performed well in the abrasive testing applications,
generating effective abrading from the start.
